The present invention relates to a living body optical measurement system and an imaging method in the system and more particularly, to a living body optical measurement system and an imaging method which are adapted to measure in vivo information by using light and to image results of measurement.
Desired in clinical medical treatment is a system or a method for measuring the interior of a living body with ease without adversely affecting the living body. Measurement using light is very effective to the desirability. The first reason for this is that the oxygen metabolic function inside the living body corresponds to the concentration of a specified pigment (hemoglobin, cytochrome aa3, myoglobin or the like) in the living body, that is, the concentration of a light absorber and the concentration of the specified pigment can be determined from an absorption amount for light (having wavelengths of from visible rays to near infrared rays). The second reason is that light can be handled easily by optical fibers. The third reason is that optical measurement does not harm the living body when used within the safety standards.
A system which utilizes the advantages of the living body measurement based on light to irradiate light having wavelengths of from visible rays to near infrared rays on a living body and measure the interior of the living body from reflection light at a location about 10 to 50 mm distant from an irradiation position is described in, for example, patent disclosures of JP-A-63-277038 and JP-A-5-300887. Also, a system for measuring CT images of the oxygen metabolic function from light transmitting through a living body having a thickness of 100 to 200 mm, that is, an optical CT system is described in, for example, patent disclosures of JP-A-60-72542 and JP-A-62-231625.
Known as a conventional living body optical measurement system is an oximeter for measuring the degree of oxygen saturation in the artery (JP-A-55-24004). The oximeter is a system in which light having a plurality of wavelengths is irradiated on a living body, the transmitting light intensity or reflection light intensity from the living body is measured, and spectroscopic characteristics of reduced hemoglobin (Hb) and hemoglobin oxide (HbO2) and pulsation waves are utilized to calculate the degree of oxygen saturation in the artery.
Also known as a method for measuring the degree of oxygen saturation in tissues of a living body (average degree of oxygen saturation in both the artery system and the vein system) and the hemodynamic amount is a method by Jobsus et al (JP-A-57-115232). This method utilizes spectroscopic characteristics of Hb and HbO2 to measure the degree of oxygen saturation and the hemodynamic amount in tissues of a living body.
To add, in the present specification, transmitting light, reflection light and scattering light are not particularly discriminated from each other and the intensity of light which is emitted from a light source, interacts with a living body and then is detected by a photodetector is called the transmitting light intensity.
Problems that the invention is to solve are three as below.